1. Field of the Invention
The present invention relates a method of manufacturing that eliminates lead to shield shorts at the ABS of an MR read head and, more particularly, that eliminates electrical shorts which are caused by conductive material bridging between conductive leads and conductive shields at the ABS.
2. Description of the Related Art
A magnetoresistive (MR) read head employs a magnetoresistive thin layer, hereinafter referred to as an MR stripe, which changes resistance in response to a magnetic field from a rotating magnetic disk. The change in resistance forms the readback signal produced by the MR head. The readback response of the MR stripe is based on how well the resistance change follows the change in magnetic field strength.
In a typical MR read head, the MR stripe is a thin film layer which is sandwiched between bottom and top insulation gap layers G1 and G2 which, in turn, are sandwiched between bottom and top shield layers S1 and S2. The distance between the shield layers is called the "read gap". The smaller the read gap, the greater the resolution of the MR read head.
The MR stripe is typically fabricated from Permalloy, which is NiFe. Preferably, NiFe is also used to fabricate the shield layers S1 and S2 of the MR read head. Lead layers L1 and L2 of the MR read head, which are connected to opposite lateral ends of the MR stripe, are fabricated from a conductive material, such as Ta, Au or Ru. The first and second gap layers G1 and G2 of the MR read head, which separate the lead layers L1 and L2 from the first and second shield layers S1 and S2, are fabricated from an insulative material, such as Al.sub.2 O.sub.3. The insulative capability of the gap layers prevents an electrical short between either of the lead layers and either of the first and second shield layers. If an electrical short occurs, sense current is shunted to one or more of the shield layers, causing a decrease in the amount of sense current conducted through the MR stripe. The result is that readback signal amplitude may be significantly reduced.
After the MR stripe, the pair of conductive leads, the pair of insulation gap layers G1 and G2, and the pair of shield layers S1 and S2 are fabricated, all of these layers are lapped to form the ABS. After lapping, each of the MR stripe, the conductive leads L1 and L2, the first and second insulative gap layers G1 and G2, and the first and second shield layers S1 and S2 has an edge surface which forms a portion of the ABS. As is known, the lapping process sometimes streaks conductive material between the conductive leads and the shield layers to form a current-conducting short circuit path therebetween. This conductive material may streak across one or more of the first and second insulative gap layers G1 and G2. In the prior art, streaking that results from the lapping process has significantly decreased the production run yields of MR read heads. MR read heads which are tested and found to have electrical shorts are simply discarded. This is because an electrical short circuit shunts the sense current to the shields, and produces noise during operation of the MR read head. It would be desirable if the yield from these production runs could be increased by salvaging the MR read heads which have electrical shorts across their insulative gap layers at the ABS.